You should only look at the latest election to see what could and should be changed. The UK needs a voting reform that would decrease Parliament error rate and increase voter happiness and satisfaction. This is most easily done by shifting away from first-past-the-post to either Mixed-Member Proportional Representation or Single Transferable Vote. Take a look into that and it should be rather easy to write your essay.
If in doubt, turn to CGP Grey's Youtube channel, which should explain everything in considerably more detail then myself.